The invention relates to a data carrier which can be operated in a contact-bound mode and in a contactless mode and which includes the means specified hereinafter, namely a transmission contact and a further transmission contact which are both mechanically accessible from outside the data carrier, and at least one transmission coil which is inductively accessible from outside the data carrier and which serves to receive a useful HF signal in the contactless mode of the data carrier, and a circuit which has a contact terminal connected to the one transmission contact and which has a further contact terminal connected to the further transmission contact and which includes supply voltage generating means to which a received useful HF signal can be applied and by which a supply voltage for various circuit sections of the circuit of the data carrier can be derived from an applied useful HF signal.
The invention further relates to a circuit for a data carrier which can be operated in a contact-bound mode and in a contactless mode and which includes the means specified hereinafter, namely a contact terminal and a further contact terminal which are both adapted to be connected to transmission contacts which are mechanically accessible from outside the data carrier, and two coil terminals which serve for connection to a transmission coil which is inductively accessible from outside a data carrier and which serves to receive a useful HF signal in the contactless mode of the circuit, and supply voltage generating means to which a received useful HF signal can be applied and by which a supply voltage for various circuit sections of the circuit can be derived from an applied useful HF signal.
Such a data carrier of the type defined in the first paragraph and such a circuit of the type defined in the second paragraph are known, for example from the document WO 96/38814 A1.
In the present context reference is made particularly to the known data carrier shown in FIG. 3 of the document WO 96/38814 A1 and described in the corresponding description. A problem encountered with this known data carrier, which as regards its contact-bound operation complies with the international standard ISO 7816, is that in the contactless mode of the data carrier, when a supply voltage is generated with the aid of the supply voltage generating means, a potential difference occurs between two transmission contacts on which the two supply potentials which define the supply voltage appear and which are not required for operation in the contactless mode. If in this situation an electrically conductive object, such as for example a coin or a ring on a finger of a user""s hand, comes into electrically conductive contact with one of these two transmission contacts, a short-circuit occurs between these two transmission contacts, which causes the above-mentioned potential difference to break down, as a result of which the supply voltage generated with the aid of the supply voltage generating means is at least affected very strongly and may even totally break down. Eventually, this results in at least a disturbance or even a disruption of the contactless mode of operation, which is obviously undesirable and inadmissible.
It is an object of the invention to preclude the afore-mentioned problem and to provide an improved data carrier and an improved circuit for a data carrier in a simple manner and with the aid of minimal means.
According to the invention, in order to achieve the afore-mentioned object in a data carrier of the type defined in the first paragraph, the circuit includes switching means, and of the one contact terminal connected to the one transmission contact and the further contact terminal connected to the further transmission contact at least one of these two contact terminals is connected to the switching means, and the switching means enable the application of a potential, which appears as a result of the supply voltage generated by the supply voltage generating means, to this at least one contact terminal to be inhibited. Thus, it is achieved with only a minimal additional expenditure that with a data carrier in accordance with the invention it is always guaranteed that the in the contactless mode of the data carrierxe2x80x94in which a supply voltage is generated with the aid of the supply voltage generating meansxe2x80x94the application of a supply potential to a respective transmission contact is inhibited, so that it is always assured that no short-circuit can occur between two supply potentials of different value, which further has the advantage that in the contactless mode of the data carrier this mode of operation cannot be disturbed or disrupted in an undesired manner.
In a data carrier in accordance with the invention having the characteristic features defined in the independent claim 1 it has proved to be advantageous if, in addition, the measures defined in the dependent claim 2 are taken. Such an embodiment is advantageous in view of a simple implementation of the circuit, particularly when the circuit is implemented in the form of an integrated circuit.
In a data carrier in accordance with the invention having the characteristic features defined in the independent claim 1 it has further proved to be advantageous if, in addition, the measures defined in the dependent claim 3 are taken. Such an embodiment has proved to be particularly advantageous in practical tests. It is to be noted that the measures defined in the dependent claim 3 can also be applied advantageously to a data carrier in accordance with the invention having the characteristic features defined in the dependent claim 2.
In a data carrier in accordance with the invention having the characteristic features defined in the independent claim 1 it has further proved to be particularly advantageous if, in addition, the measures defined in the dependent claim 4 are taken. Such an embodiment has proved advantageous in view of a particularly high reliability as regards the cut-off of an undesired potential from a transmission contact when a desired mode of operation of a dual-mode data carrier is active. It is to be noted that the measures defined in the dependent claim 4 can also be applied advantageously to data carriers in accordance with the invention having the characteristic features defined in the dependent claim 2 and 3.
In a data carrier in accordance with the invention having the characteristic features defined in the dependent claim 4 it has proved to be very advantageous if, in addition, the measures defined in the dependent claim 5 are taken. This has proved to be particularly advantageous in view of a very high reliability as regards the cut-off of an undesired potential from a transmission contact when the contact-bound mode is active.
According to the invention, in order to achieve the afore-mentioned object, a circuit of the type defined in the second paragraph is characterized in that the circuit includes switching means, and of the one contact terminal adapted to be connected to the one transmission contact and the further contact terminal adapted to be connected to the further transmission contact at least one of these two contact terminals is connected to the switching means, and the switching means enable the application of a potential, which appears as a result of the supply voltage generated by the supply voltage generating means, to this at least one contact terminal to be inhibited. In this way, advantages which correspond to the advantages described hereinbefore for a data carrier in accordance with the invention having the characteristic features defined in the independent claim 1 are obtained for a circuit in accordance with the invention.
The advantageous variants of a circuit in accordance with the invention, which variants have the characteristic features defined in the dependent claims 7 to 10, yield advantages which correspond to the advantages described above for the advantageous variants of a data carrier in accordance with the invention, which variants have the characteristic features defined in the dependent claim defined in the dependent claims 2 to 5.
The afore-mentioned aspects as well as further aspects of the invention will be apparent from the embodiments described hereinafter by way of examples and will be elucidated with reference to this embodiments.